Relapse to alcoholism remains a vexing clinical and national health problem. Efforts to match alcohol dependent patients to specific treatments based on their clinical characteristics have produced mixed results. Pharmacogenetics (the study of genetic influences on therapeutic response to drugs) offers a powerful new tool to match specific elements of an individual patient's complex genetic blueprint with targeted pharmacotherapies to which that individual may optimally respond. The purpose of this proposed research is to apply pharmacogenetic techniques to predict which alcohol dependent patients will respond favorably to a trial of a selective serotonin re-uptake inhibitor (SSRI) for the prevention of alcoholism relapse. Our central hypothesis is that genetic differences affecting serotonin transporter function will influence an alcohol dependent individual's treatment response to the SSRI, citalopram. To test this hypothesis, we will perform a 14-week, randomized, double blind, parallel group comparison of citalopram and placebo in treatment seeking outpatients who meet DSM-IV criteria for alcohol dependence. All subjects will receive a single Motivational Interview and 9 brief sessions of a manual-guided Compliance Enhancement Therapy designed to promote treatment adherence and enhance motivation to quit or cut down on drinking. Post-treatment follow-up assessments will be conducted at 4, 12 and 24 weeks. Subjects' DNA will be genotyped to determine allelic variants in the promoter region of the serotonin transporter gene that have been found to markedly affect serotonin reuptake and influence treatment responsiveness to SSRIs. We predict that individuals who carry two long variant alleles (1/1 homozygotes) of this polymorphism will exhibit a significant reduction in drinking days in response to citalopram compared with patients homozygous for the short variant allele (s/s homozygotes). To our knowledge, this will be the first study conducted in alcohol dependent patients to test whether pharmacogenetic differences in the function of the serotonin transporter (the site of action of these medications) influence the treatment response to a SSRI in nondepressed women and men. The study is designed to maximize the likelihood of finding treatment efficacy for citalopram over placebo by excluding subjects with severe alcohol dependence and marked impulsive traits in which SSRIs have not been found to be effective, controlling the exposure to the concomitant psychosocial intervention to minimize a psychotherapy ceiling effect, and by controlling the potential moderating effects of sex and cigarette smoking. The successful completion of this single center study may lead to future multicenter trials in more heterogeneous populations, and to studies using serotonin receptor subtype-specific medications.